The present invention relates to a filtration system for aquariums and more particularly to a filtration system in which the roots of a terrestrial plant grow into the filtration means and utilize the waste products from the aquarium carried by the water.
Filtration is an important consideration in an aquarium which serves the following functions:
To remove unwanted gross solid particulate matter such as uneaten food and feces (mulm) from the water so as to keep it clear. PA1 To remove unwanted coloring matter, which gradually accumulates in the water, turning it yellow and then brown if it is not frequently changed. PA1 Occasionally to remove algal or bacterial "blooms", which cloud the water and make it opaque, green, or milky in appearance. Algae utilize oxygen and severe algal contamination depletes the supply of oxygen and can result in oxygen starvation of the fish. In addition, some algae produce toxins which are poisonous to the fish. PA1 To remove invisible, colorless dissolved matter such as ammonia and nitrites that are poisonous to the fish in all but minute amounts.
An ordinary coarse filter material such as synthetic filter floss or filter pads of various types only copes with the first item above when it is first set up or if the filter is frequently cleaned out, but as time goes on an old filter bed may start performing some of the other functions as well, particularly removal of dissolved matter. This is because bacteria grow in it that convert unwanted products of fish life, such as those listed, to harmless ones--particularly nitrates--which are utilized by the plants.
The main toxic material produced by the breakdown of excreta, uneaten food, etc., is ammonia. This is converted to nitrites by bacteria such as Nitrosomonas, then by further bacterial action, involving Nitrobacter, the nitrites are converted to nitrates. Both ammonia and nitrites are harmful to fish, even in minute amounts (200 to 300 parts per million), and can be monitored by suitable test kits. However, if bacteria growth is not present, the decomposition of uneaten food and mulm produces toxic substances which may kill the fish.
Another popular filter material, activated carbon or charcoal, performs, in particular, removal of coloring matter and dissolved matter right from the start. Fine granulated so-called gas grade charcoal has an enormous adsorptive surface on which chemicals of all descriptions may be adsorbed, and on which bacteria may also grow. These bacteria may interfere with the charcoal's main function, although a balance often seems to be achieved, with quite old charcoal continuing to adsorb chemicals and grow bacteria. Eventually, it will clog up and have to be replaced, but it can take up to more than half its own weight of adsorbed materials with it. When in a semi-clogged condition, both filter wools and activated charcoal extract finer and finer materials and may assist in removal of algae. Most of the desirable functions of a simple filter will be performed if it is provided with a bed of fine filter floss and activated charcoal. The charcoal is usually placed between layers of floss, so that it cannot escape into the aquarium.
The simplest filter is a box filter which is disposed inside the aquarium and is generally placed in a back corner where it is less visible. The box is usually a transparent plastic container filled with a combination of filter wool and charcoal (sometimes with gravel). A layer of charcoal is sandwiched between the filter wool, with gravel on the bottom to weigh down the container.
Other filters may hang inside the top of the tank, or outside the top of the tank, and are then known as "inside" or "outside filters. An airlift conveys water into the filter using a simple injection of air into a plastic tube. In an inside filter, the airlift curves over at the top, the air-water mixture flows into the filter and the water passes down through the filter bed and escapes back into the tank via perforations at the base of the filter. In an outside filter the water is drawn into a tube by an airlift in the tank and so returns to the tank, while one or more siphon tubes convey water from the tank to the filter, where it passes through the filter bed (or beds) and back into the tank. It is preferred that a pump be used with an outside filter to draw water up from the tank, pass the water through the filter and return the water to the tank.
U.S. Pat. No. 4,169,050 discloses a wastewater treatment for a pond which has floating aquatic plants, submerged bio-web substrates and aeration by submerged perforated air diffusers and a floating aerator.
A terrarium/aquarium combination is disclosed in U.S. Pat. No. 4,754,571. The plants in the terrarium are separated from the aquarium by a vertical partition. The combination provides an apparatus for humidifying indoor air. Included are filter plates beneath the terrarium substrate and in the aquarium.
A fish farm and hydroponic greenhouse are disclosed in U.S. Pat. No. 5,046,451. The fish tank is equipped with a submerged biofilter with vertical channels and underlying air lines. Air bubbles rise in the channels to agitate and aerate the water.
U.S. Pat. No. 5,121,708 discloses a hydro culture crop production system for raising land and aquatic plant and animal crops.